Epistemica

Mamdani’s announcement that the NYPD will arrest Immigration and Customs Enforcement (ICE) agents who violate New York law has raised the immediate question of whether a city or state can actually arrest a federal officer and start a criminal case. The short answer is, of course, yes. Federal agents can commit state crimes, and it is the state’s responsibility to prosecute such crimes. The caveat is that federal agents are immune to prosecution when the officer’s conduct is considered protected federal activity. Federal officers are not categorically immune from state criminal law, and the Supreme Court has said so for more than a century. The harder part is sustaining a prosecution once the case moves into federal court, but the possibility of arrest and charging is real and has historical precedent.

The constitutional starting point is Article VI, specifically the Supremacy Clause, which makes federal law “the supreme Law of the Land” and prevents states from sabotaging lawful federal programs. There is, as a result, Supremacy Clause immunity. In its classic formulation in In re Neagle, 135 U.S. 1 (1890), the Court protected a U.S. marshal from California murder charges because he was performing a federally assigned duty and his use of force was necessary and proper to that duty. Later cases described the test in the same two parts: the officer must have been doing something authorized by federal law, and the manner of doing it must have been necessary or at least objectively reasonable in the circumstances. If both prongs are satisfied, state criminal law must give way.

That rule, however, cuts both ways. The Court has also said that federal officers do not receive “blanket immunity” for everything they do while on the clock. In Tennessee v. Davis, 100 U.S. 257 (1879), a federal revenue officer involved in a fatal shooting during an enforcement action was allowed to remove the case to federal court, but the premise of the decision was that state prosecutions sometimes may proceed and therefore need a federal forum. In Mesa v. California, 489 U.S. 121 (1989), a postal employee could be charged in state court for on-duty driving that caused a death, unless he could actually show a federal defense.

There is also a long record of states charging federal officers whose conduct looked less like law enforcement and more like ordinary state-law crime. Nineteenth-century states brought actions against customs and revenue officers when seizures were heavy-handed or when force was thought to be excessive. Twentieth-century states charged federal officers with assault, manslaughter, or trespass when raids went wrong or when officers entered property without a defensible federal basis. Federal courts sometimes released the officers on immunity grounds, but sometimes they did not, especially when the force used appeared unreasonable or when the officer’s story was disputed. That mixed record matters for New York because it shows that a state arrest is a recognized instrument of “pushback” when federal officers behave egregiously.

Thus, if an ICE team executes a federal warrant at the right location, detains only the person named, and uses proportionate force, Supremacy Clause immunity should attach. New York could not use its assault or unlawful-imprisonment statutes to second-guess federal immigration policy. If, however, agents detain bystanders with no immigration nexus, hold U.S. citizens for nearly a day without charges, or enter private premises without a colorable federal authority, then the conduct begins to look like ordinary state crimes such as unlawful imprisonment, trespass, or even official misconduct. New York officials have already responded to such incidents by creating reporting mechanisms for aggressive federal raids, which shows that state actors are building factual records suitable for criminal process.

In that second category NYPD officers would be on solid legal ground to make an arrest. State and local police retain their usual power to arrest when they have probable cause that a state crime occurred in their jurisdiction. Federal employment does not erase that power. The arrested ICE agent would then have a well-known federal escape hatch: 28 U.S.C. § 1442 allows federal officers to remove the prosecution to federal court if the case relates to acts under color of federal office and if the officer asserts a colorable federal defense. That statute exists precisely because Congress understood that states sometimes do, and sometimes should, bring such cases. Once in federal court, the agent would argue that he was acting within federal authority in a way that was necessary and proper, invoking Neagle, Davis, and the later immunity decisions.

This is where Mamdani’s plan becomes, as he implied, more difficult but not unlawful. The state can arrest. The state can charge. The state can force the factual dispute into a judicial forum. The federal court may eventually dismiss on immunity grounds, especially if the agent can show a reasonable belief that he was carrying out a federal order. Courts have done exactly that in cases involving mistaken trespass during wildlife monitoring and in prosecutions of federal officers who used force during contentious federal operations. The key is factual development. If video, officer reports, and witness statements show that the ICE agent knew he lacked authority, or that he used force that cannot be justified by the situation, the immunity defense becomes weaker, and a federal judge may allow the case to proceed to trial.

From a policy standpoint, the arrest threat is significant even if convictions are infrequent. After all, it signals that New York will treat federal immigration officers in the same way it treats any other actor who unlawfully restrains city residents. It then creates a record that can be shared with state oversight bodies and with the Attorney General, both of which have shown interest in documenting overreach during immigration raids. With the recent history of ICE agents acting beyond their authority, it seems that there are already documented instances of such agents breaking the law in ways that would make them eligible for legitimate arrest by the NYPD.